As is known, in the conventional structure of these pizoelectric mechanisms, the striker hammer plays on the axial hollow of the interior telescopic body, and in the rest position it is found spaced from the piezoelectric element, due to the existence of retention means, will be described hereinafter.
When a manual compression force Is exerted on the telescopic assembly to cause the lighting, which is accomplished by overcoming the action of the spring which assists the telescopic assembly, the compression of a second spring simultaneously takes place, which shall subsequently activate the striker hammer at the moment of release, thus creating the impact energy of the hammer.
The guiding means of the striker hammer are defined by a pair of confronted longitudinal grooves, which run through the wall of one of the tubular bodies, the grooves housing two diametrical projections of the striker hammer.
In the condition of rest of the mechanism, the striker hammer is found retained by its transversal projections, in two notches, each open at a side of the respective longitudinal groove of said tubular body, being inserted in the notches when the striker hammer is forced to effect a rotational movement. In order that the striker hammer performs a small rotation, both for exiting from the retention notches and for entering the same after the impact, to originate the rearming of the mechanisms, at the end of the compression run of the telescopic assembly, and during the distension of the same, respectively, the diametrical projections of the striker hammer are pressed by the ramp edges of two windows provided on the other telescopic body, where said projections also play.
In the U.S. Pat. No. 5,262,697, a mechanism is described of the previously defined type, by means of which a perfect guiding of both telescopic bodies is achieved, having said bodies a totally symmetrical geometry of easy construction, in which the guiding means is external to the position of maximum separation of the telescopic assembly recovery spring and of the spring which activates the striker hammer, which is additionally totally guided throughout its travel.
The mechanism of this Patent, U.S. Pat. No. 5,262,697, achieves the elimination of the induction effects created at the moment when the spark is produced, having been provided that the exterior spring occupies a position which is axially spaced from the piezoelectric element. Likewise, the path of the electric circuit is shortened, with the intervention of the least number of elements possible and it being possible to use nonconductive plastic and to reduce the production costs, as well as achieving a perfect mixing of the gas with the air, prior to the moment when the gas lighting spark is produced, optimizing the combustion. Additionally, the mechanism of document U.S. Pat. No. 5,262,697 also ensures a perfect seating of the hammer on the piezoelectric element by the intervention of a stopping part or base of the striker, so as to achieve greater intensity and sparking time.
The Spanish Patent application P-8902741, describes and claims a piezoelectric mechanism for gas lighters by means of which the elimination of angular movement between both telescopic components is achieved, providing on the exterior body, a pair of projections which act with a key function, playing in the interior of the actual grooves provided on the interior telescopic body for the axial movement of the striker hammer. Due to this, said grooves need to be of greater length than that necessary for the guiding of the hammer. The shortening of the path travelled by the electric current is achieved, since the current only circulatates through the anvil, piezoelectric element, stopping part of the striker hammer and exterior telescopic body, on the contrary to the other previous mechanisms in which the electric current also passes through the springs which assist the striker hammer and the telescopic assembly.
In the piezoelectric mechanisms of the type previously described, the spring which assists the striker hammer, is partially or totally guided inside the telescopic body which houses the striker hammer, abutting its other end on a cover which is attached on the free end of said body, since it is equipped with projections with sawtoothed section, the projections being inserted in respective lateral windows existing on the confronted walls of the telescopic body, becoming immobilized in said fixed position.
Through the windows in the telescopic body with essentially quadrangular transversal section and which houses the striker, in which the diametral projections of the striker are guided, foreign particles, humidity and dust may penetrate, which may produce the obstruction and corrosion of the spring inside the telescopic body, as well as producing pollution and the consequent increase of friction, for example on the ramps on which slide the diametrical projections of the striker slide, apart from the possibilities of generation of parasite electrical currents induced by the presence of dust and/or humidity, all of which may cause a deterioration of the capacity or even result in the impossibility of the generation of lighting sparks, which may also cause a blocking of the mechanism, which is specially hazardous if the blocking is produced when the gas valve is open.
On the other hand, during the assembly process of the piezoelectric mechanisms of the type described in documents U.S. Pat. No. 5,262,697 and EP-A-0172973, the striker must necessarily be inserted in diagonal position into the exterior telescopic body, making it necessary that the interior telescopic body, which is inserted in the axial perforation of the exterior body, requires chamfered ramps on which the lateral striker projections can slide, being forced to effect a small rotation until the grooves or longitudinal guides are reached.
Though it is true that the mechanisms of documents U.S. Pat. No. 5,262,697 and EP-A-0172973 have been the basis of millions of piezoelectric mechanisms with satisfactory results, they imply the forced necessity of a positioning of the projections of the striker in diagonal direction with respect to the exterior telescopic body into which it is previously inserted, as well as the forced requirement of equipping the internal end of the interior telescopic body, with the said positioning ramps during the assembly process of both bodies. This implies a certain complication during the assembly process.